Trying to translate en-US raises a 500

[bugzilla-to-github]

This issue was created automatically by a script.

Bug 1598324

Bug Reporter: @Natim CC: @mathjazz See also: #2260

User Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:70.0) Gecko/20100101 Firefox/70.0

Steps to reproduce:

We are struggling translating to en-us in pontoon.

I guess pontoon expect it to be the source of translation, however in our case because we are not native english speakers we still need to let translator improve it

Add en-us as a translation target and try to open the resources for this locale

Actual results:

A message Oups an error occurred will show.

Expected results:

In the case of .properties files the source is not en-us anyway so it totally makes sense Same for gettext po files where template.pot doesn't need to be en_US.po